package n21;

public class Main {
    public ListNode mergeTwoLists(ListNode list1, ListNode list2) {
        if (list1 == null) {
            return list2;
        } else if (list2 == null) {
            return list1;
        } else if (list1.val < list2.val) {
            list1.next = mergeTwoLists(list1.next, list2);
            return list1;
        } else {
            list2.next = mergeTwoLists(list1, list2.next);
            return list2;
        }
    }

    public static void main(String[] args) {
        Main main = new Main();
        // ListNode list1 = new ListNode(1, new ListNode(2, new ListNode(4)));
        // ListNode list2 = new ListNode(1, new ListNode(3, new ListNode(4)));
        ListNode list1 = new ListNode(1, new ListNode(5));
        ListNode list2 = new ListNode(1, new ListNode(2, new ListNode(4)));
        ListNode listNode = main.mergeTwoLists(list1, list2);
        System.out.println(listNode);

    }
}

class ListNode {
    int val;
    ListNode next;

    ListNode() {
    }

    ListNode(int val) {
        this.val = val;
    }

    ListNode(int val, ListNode next) {
        this.val = val;
        this.next = next;
    }

    @Override
    public String toString() {
        return "ListNode{" +
                "val=" + val +
                ", next=" + next +
                '}';
    }
}